The slot value
callback-type
determines which arguments get passed to each of the callbacks. It can be any of the following values, and passes the corresponding data to the callback function:

:collection-data

(
collection data
)

:data

(
item-data
)

:data-interface

(
item-data
interface
)

:interface-data

(
interface
item-data
)

:item

(
item
)

:item-interface

(
item
interface
)

:interface-item

(
interface
item
)

:interface

(
interface
)

:full

(
item-data
item
interface
)

:focus

The pane with the current input focus.

:none

()

nil

()

callback-type
can also be a list containing any of
:focus
,
:data
,
:interface
,
:collection
,
:item
.

The
item-data
variable is the item's data if the item is of type item, otherwise it is the item itself, as for
item.
The
item
variable means the item itself. The
interface
is the
element-interface
of the element.
collection
is the element's collection, if there is one.